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Henrietta Swan Leavitt… and Dolls

Happy Ada Lovelace Day [1] everyone!

Because my birthday was this past weekend, I wanted to tell you about one of the great women of astrophysics: Henrietta Swan Leavitt.

What does this have to do with my birthday? I can hear you asking that. See, my parents are wonderful, thoughtful, creative geeks. And they got me an American Girl doll for my birthday. (YES, my birthday this year. YES, I’m an adult). But then they dressed her up like Henrietta Swan Leavitt. She even has accessories!

(Reply to this post to vote for my parents to create a whole line of women scientist outfits for American Girls dolls! I sure do…)

My American Girl Woman


I was in transports of delight. Yes, my mother sewed those new clothes for her. (The skirt is leftover fabric from my prom dress oh so many years ago.). My father worked on the accessories:

Henrietta Swan Leavitt

Henrietta Swan Leavitt made it possible for us to measure the size of the Universe.

Yup. read that again. Henrietta Swan Leavitt made it possible for us to measure the size of the Universe.

Ostensibly she was working as a “computer” (what women who did the computational or classification work in astronomy were called in those days) for Dr. Edward Pickering at the Harvard College Observatory.

It was there, rubbing elbows with other famous women of astrophsics like Annie Jump Cannon [4], as she was classifying the sizes of variable stars in the Magellanic Clouds that she discovered the period-luminosity relationship in Cepheid variable stars [5].

Variable stars are, as they sound, stars that vary in brightness. What Henrietta discovered, is that for Cepheid variables, the brightness of the star (luminosity) and the period (time between brightest moments) are related. The longer between “blinks” the brighter the star. This means that if you can see a star varying and time between the “blinks” you can figure out how bright that star actually is, not just how bright it looks. (Remember that farther away stars look dimmer, but if you got closer to them they’d look brighter).

By knowing how bright a star truly is, you can accurately measure the distance to that star by how dim it appears to be. Which means you can now measure the distances to things outside our galaxy.

Go read up some more… and let’s investigate the rest of those women computers from Pickering’s lab. Did they all make awesome discoveries? Margaret Harwood, Mollie O’Reilly, Edith Gill,  Evelyn Leland, Florence Cushman, Marion Whyte, Grace Brooks, Arville Walker, Johanna Mackie, Alta Carpenter, Mabel Gill, and Ida Woods.

Want More?

*In case you’re curious, the doll is the newest historical American Girl: Caroline, with her hair pulled back in a bun.

Henrietta Swan Leavitt from the AAS [6]

Cepheid Variable Stars [5]


~ A l i c e !